Students develop fertilizer from shōchū distillation remnants

KUMAMOTO – Students in Kumamoto Prefecture have developed a low-cost method to cultivate photosynthetic bacteria for use as fertilizer using the distillation remnants of shōchū, a traditional Japanese liquor.

The student researchers, led by Aoi Koga, 24, from Sojo University’s Graduate School of Engineering in the city of Kumamoto, hope their method will help farmers cut their use of chemicals and distillers save money through the reuse of the remnants left over from the distillation process called shōchū kasu.

In 2016, Koga produced a liqueur targeted at young women in collaboration with a distiller of rice-based Kumajochu shōchū, a specialty of the Hitoyoshi Kuma area in Kumamoto Prefecture.

At that time, she realized that disposing of shōchu kasu left after the distillation of mash made from fermented rice cost the shōchu-making industry millions of yen a year.

From her research, launched in April the same year, Koga found that the distillation remnants were rich in citric acid, which can be used to cultivate photosynthetic bacteria.

She and the other students, who were mentored by professor Hitoshi Miyasaka, an expert in the study of photosynthetic bacteria, tried to find the best method to grow it.

As a result of their research, which lasted for about a year, Koga’s team discovered the most stable conditions for cultivating the bacteria to ensure the best quality and increase harvests.

In April this year, Koga established a startup called Ciamo with three others to make and sell a photosynthetic bacteria culture kit, which contains the bacteria and shōchū kasu-based broth.

Ciamo was able to set the price of the kit, dubbed “Kuma Red,” at about half the price of similar products thanks to the use of the low-cost materials. Some 40 farmers, mainly in the prefecture, have purchased the kit. The company aims to achieve ¥300 million in sales in the coming three years.

It is estimated that if a rice farmer uses fertilizer made using photosynthetic bacteria, its profit would increase by about ¥90,000 per 1,000 sq. meter of field thanks to a decline in the use of chemical alternatives and a rise in crop production.

Shōchū producers also welcome the development of the method to recycle their distillation residue, which is designated as industrial waste, because disposing of it by traditional methods is costly, the head of Toyonaga Shuzo, a distiller in the town of Yunomae, said.

Expressing hope to expand into overseas markets, Koga, who serves as president of Ciamo, said, “We’re eager to use the power of microbes to reduce the use of pesticides and chemical fertilizers, even if only slightly.”